Giant Enlarged Circular Metallo-Rings.

Facilitated by the tert-butyl substituent in a C2-symmetric bis(hydrazone), along with the incorporation of 3d ions, oxalate, carbonate, and sodium ions, a homononanuclear dysprosium ring [Dy9(L1)3(μ3-O)4(μ3-AcO)3(μ2-AcO)6 (μ2-COO)3(DMF)3]·3DMF·1MeOH·6H2O (Dy9) and a heterooctaoctacontanuclear dysprosium-zinc-sodium ring [Dy48Zn24Na16(L2)24(μ6-C2O4)8(μ4-C2O4)18(μ4-CO3)8(μ4-AcO)34(μ4-COO)16(DMF)10(H2O)28]·2Cl·46DMF·38MeCN·82H2O (Dy48Zn24Na16) were synthesized. Compounds Dy9 and Dy48Zn24Na16 exhibit distinct single- and triple-stranded cyclic topologies, in which the bis(hydrazone) ligands L1 and L2 adopt different conformations and exhibit distinct metal coordination modes. While 12 acetate molecules serve as terminal coligands occupying the remaining coordination sites in assembly Dy9, hexacosuple-C2O42-, octuple-CO32- and triacontatetraple-AcO- bridges act as mixed oxoanion templates to form Dy48Zn24Na16 by linking hexanuclear Dy6Zn3Na2(L2)3 building blocks. Sixteen sodium ions act as a tertiary template, filling the internal void of the latter structure. Furthermore, it was observed that the structural modifications largely influence the zero-field magnetic relaxation behavior. This work presents a new approach for constructing C2O42--, CO32-- and AcO-- bridged heterometallic metallosupramolecular rings through the deliberate addition of oxalate, carbonate and acetate for magnetic dynamic studies.